Tbh I bet they would keep their relationship secret just for fun. Like they'd keep up their argumentative public appearance then they'd go somewhere private and suck faces. Bonus points if Phichit catches them and does the signature reaction face.
Yesss, bonus bonus points if they have a facade of disliking each other and thats largely where Seung’s seemingly cold exterior comes from. But behind closed doors he’s super touchy feely (and though still near expressionless it’s clear he has a lot of affection for JJ) and JJ’s like “Man you really made me think you hated my ass for a second there” and Seung’s like “You may be a pompous asshole, but no one could hate That Ass. Also i love you or whatever”
oK STOP ME NOW.